Technical Field
Embodiments of the subject matter disclosed herein generally relate to a downhole gauge that is attached to a carrier mechanism and a method for fixing the downhole gauge to a tubing or casing string.
Discussion of the Background
A downhole gauge may be a device used to collect data (e.g., pressure, temperature, etc.) in downhole environments, such as, for example, inside of wells used for oil and gas extraction. Downhole gauges may contain one or more sensors, for example, a pressure sensor, a temperature measuring device, etc. A downhole gauge that has been lowered into a well may be fixed to the casing or tubing of the well. Several gauges may be connected together, top to bottom, along with other survey equipment, along the casing or tubing.
FIG. 1 depicts an exemplary casing 100 that has a downhole gauge 110 attached to it. Casing 100 has a cylindrical shape with its ends 104 and 106 threaded to connect to other casings. Casing 100 has a body 102 in which a bore 108 is formed through which oil and/or gas are flowing when deployed in the well.
During various stages of drilling, production and/or maintenance, various parameters around or inside the casings need to be known, as for example, the ambient pressure and/or temperature where the casing is located. In this regard, it is known that both the pressure and temperature are very high at the depths at which the casings are placed. A gauge 110 is then attached to the casing in one of two ways.
FIG. 1 shows gauge 110 being completely embedded in a chamber 112 formed in the body 102 of casing 100, as disclosed in U.S. Pat. No. 6,655,452. Various mechanisms may be used for fixing gauge 110 to body 102, e.g., a plate 114 being screwed to body 102 over gauge 110. This configuration requires that a recess is cut into the casing.
An alternative is to mount a gauge 120 inside body 102 as illustrated in FIG. 2, and disclosed in U.S. Pat. No. 7,090,010. In this case, a hole with a threaded region 122 is formed at end 106 of body 102 so that one end 120A of gauge 120 screws into it while the other end 120B of gauge 120 is hanging freely inside chamber 124. This configuration exhibits at least two disadvantages. One is that the gauge is disposed inside the tubing and, thus, the flow area inside bore 108 is reduced. The other one is that no electrical line can be attached to the gauge.
In addition, both configurations illustrated in FIGS. 1 and 2 have shown that an electrical connection that sometimes needs to be made between the gauge and a corresponding electrical line (usually called tubing encased cable, TEC) is cumbersome, if possible, due to the lack of clearance between the gauge and the casing. Further, these systems do not have a high pressure rating because of the gauge location or the lack of good seals between the gauge and the bore.
Thus, there is a need to provide a new gauge carrier mechanism that overcomes the above noted problems, makes the installation of the gauge simple, and/or prevents excessive vibrations of the gauge.